Integrated circuit devices are commonly manufactured using a process known as photolithography. In photolithography, a photoresist layer is first deposited on a wafer substrate. Radiant energy, such as ultraviolet light, is then projected onto the photoresist layer through a template in the form of a mask or reticle having the desired pattern. The photoresist layer is then developed to remove either the exposed portions or the unexposed portions, to form a resist mask on the substrate. The resist mask can then be used to protect underlying areas during later deposition or etching processes.
An important component of the photolithographic apparatus is the reticle, which provides the pattern and layout corresponding to the various integrated circuit features. Typically, the reticle is a transparent glass plate with a layer of opaque or semi-opaque material coated thereon forming the pattern. It is critically important that the surfaces of the reticle, especially the coated surface, be protected from damage or contamination, since any such defects or contamination may be projected onto the photoresist layer during exposure, thus leading to a finished integrated circuit device of unacceptably diminished or even unusable quality.
Specialized carriers have been developed to protect a reticle from physical damage and contamination during storage and transport. These carriers typically comprise an enclosure having various reticle contact portions therein for supporting and restraining the reticle from movement. The reticle is usually manually positioned on support surfaces within the enclosure, and the reticle is then engaged and more closely restrained against movement by restraint members attached within the enclosure. These restraint members are typically designed to engage the reticle at its edges. A problem, however, has been that a person initially manually positioning the reticle on the support surfaces may fail to place the reticle in the proper position for engagement by the restraint members, or may inadvertently cause the reticle to be dislodged from its proper positioning before it is engaged by the restraint members. If the reticle is out of position a sufficient distance, the restraint members may then engage the reticle on its surfaces rather than at its edges, thereby causing scratching or other physical damage to the reticle.
What is needed is some type of structure or device for ensuring proper self positioning of a reticle within a reticle carrier to prevent damage during engagement by restraint members.